# year    value 
 1980 -0.4736201 
 1981 -0.2406619 
 1982 -0.3809293 
 1983 -0.6306444 
 1984 -0.518469 
 1985 -0.4577459 
 1986 -0.2941672 
 1987 -0.2884573 
 1988 -0.1718148 
 1989 -0.05465601 
 1990 0.004073001 
 1991 -0.2944029 
 1992 -0.4009577 
 1993 -0.4905751 
 1994 -0.2178375 
 1995 -0.03212382 
 1996 -0.06812243 
 1997 0.09777983 
 1998 0.05389456 
 1999 0.1140064 
 2000 0.2949607 
 2001 0.357353 
 2002 0.2646391 
 2003 0.4638568 
 2004 0.3370336 
 2005 0.9365567